Allow tracing with fork/wait (#15184)
Summary:
There is still limitation on this: if a script module is somewhere
in the trace, the inputs/outputs can only be tensors or tuples of
tensors.
resolves #15052
Pull Request resolved: https://github.com/pytorch/pytorch/pull/15184
Differential Revision: D13457691
Pulled By: highker
fbshipit-source-id: 8fe46afc41357a0eb8eadd83f687b31d074deb0e
